A trend in surgery has included minimally invasive dilation of biological tissues during surgical procedures. Minimally invasive dilation of tissues is advantageous in providing transcutaneous access to deeper anatomical structures while avoiding or minimizing the cutting or tearing of muscle and other tissues. Typically, tissue dilators include a series of tubular devices, each having round cross-sectional profiles of slowly increasing outer diameters. The first dilator in the series has a minimal cross-sectional profile and subsequent larger diameter dilators are concentrically longitudinally advanced over the previous smaller diameter dilator. Circular dilator systems have an advantage of minimal trauma to tissue as the circular dilator is advanced and turned within tissue. Subsequently advanced concentric dilators provide even dilation of tissues about a first small diameter dilator. However, at least one problem known in the art is that significant off center directional dilation of tissues is not generally provided by concentric generally cylindrical dilators. Preferential directional dilation in an asymmetrical manner is not achieved with such concentric symmetrically shaped dilator systems. Some directional dilation of tissues is provided by prior art dilator systems having round walls and off center lumens. However, such dilator systems are poorly balanced, problematic to rotate, and awkward to use and control. Some relative directional dilation of tissues may be provided by prior art dilators having oblong shapes. However, a problem known in the art is that such prior art dilator systems result in at least some disruption of tissues in all directions about the first initially placed dilator when subsequent dilators are advanced.
Another trend in some dilator systems is dilators including electrodes. Dilators including stimulating electrodes have been advocated as a useful adjunct to neuromonitoring during spinal surgery. One such surgery where neuromonitoring may be advantageous is lateral transpsoas approaches to the lumbar spine. In a transpsoas approach to the spine, nerves are in danger of being damaged during the procedure. Stimulation of one or more electrode of these prior art dilators has been used to trigger an electromyographic (EMG) response that may monitored. Triggered EMG monitoring may be beneficial in detecting proximity of a dilator electrode to neural structures during spinal surgeries, for example transpsoas approaches to the lumbar spine.
After initial approach to the spine using dilators, it is beneficial to further enlarge the wound using a retractor, forming an operative corridor to visualize and access the spine. The retractor may be used to visualize and access a disc space, for example to implant a spinal spacer into the intervertebral body space for arthrodesis.
Therefore, there has been recognized by those skilled in the art a need for minimally invasive dilation of biological tissues using a dilator system during surgical procedures which dilates predominantly in one or more directions while minimizing or completely avoiding dilation of soft tissue in at least one other direction about the longitudinal axis of a first dilator and/or guidewire.
There has also been recognized a need for preferential dilation in an anatomical anterior direction and avoidance of dilation in an anatomical posterior direction by an electrode configured dilator system during a lateral transpsoas approach to the spine. All present dilation systems have a disadvantage of requiring at least some posterior dilation relative to the first placed dilator.
Still another recognized need is for a strong, stable, and secure retractor system that may provide various configurations of operative corridors and that includes blades that may be moved independent of movement of other blades that are attached to a retractor frame.
The present invention fulfills these needs and others.